Il sab 9 ago 2025, 09:00 Zhao Liu <zhao1....@intel.com> ha scritto:
> > pub fn get<'g>(&self, _: &'g RcuGuard) -> Option<&'g T> {
> > unsafe {
> > self.raw_get().as_ref()
> > }
> > }
> > }
> >
> > Using this is a bit ugly, because you need transmute, but it's isolated:
> >
> > impl AddressSpace {
> > pub fn get_flatview(&self, rcu: &'g Guard) -> &'g FlatView {
>
> IIUC, this lifetime is using the "branded type" pattern as ParentInit.
>
No, it's much simpler (that one uses the combination of for<'identity> and
PhantomData as explained in the comment). It says that the lifetime of the
returned reference cannot exceed the guard. It's just like
pub fn get_item(&self, array: &'g [u8]) -> &'g u8 {
&array[self.0]
}
Except that the guard is only there to limit the lifetime and not to hold
data.
In addition, about rcu_read_lock_held(), I thought at C side, there're
> so many comments are saying "Called within RCU critical section" but
> without any check.
>
> So I wonder whether we should do some check for RCU critical section,
> just like bql check via `assert!(bql_locked())`. Maybe we can have a
> Rcu debug feature to cover all these checks.
>
In Rust you would just pass a &RcuGuard into the function (or store it in a
struct) for a zero-cost assertion that you are in the RCU critical section.
Paolo
> Thanks,
> Zhao
>
>
>
